The present invention relates to polymeric materials that are especially useful in the manufacture of integrated devices (IC), and in particular use in structures having a plurality of layers. More specifically, this invention is directed to carefully tuned underlayer materials for use in multilayered photoresist techniques. These materials contain multiple chemical functionalities along the same polymeric chain and have been developed to optimize their chemical and physical properties. The use of the structures allows for high resolution, high aspect ratio imaging with optical, electron beam, ion beam, x-ray, or EUV lithographic systems.
Semiconductor device manufacturing places high demands on the lithographic processes that are the means by which the submicron features are generated. New geometries and ever-shrinking dimensions of microelectronic devices dictate increased resist performance in terms of ability to produce higher resolution features with higher aspects ratio and the ability to image over topography. Currently, state-of-the art single layer resists, used with KrF lasers emitting radiation at 248 nm, allow for the commercial production of features at the dimension of approximately 200-250 nm. At dimensions smaller than this, single layer resists simply cannot effectively provide the desired resolution. Many have seen a conversion to ArF, 193 nm laser systems, and corresponding 193 nm photoresist systems as the next logical step to extend the resolution capabilities of optical lithography. This involves intensive capital investment as entirely new, multimillion dollar tool sets are needed. An alternative to switching to 193 nm lithography that will extend the lifetime, and capital investment, of the 248 nm lithography systems is to introduce a multilayer imaging approach. In the longer term, as 193 nm, 157 nm, or other imaging becomes common place, this multilayer technology is amenable such that the resolution capabilities can be extended with that wavelength as well or to be used with e-beam, ion-beam, x-ray or EUV lithographic strategies.
Multilayer resist schemes offer unique advantages over single layer resist systems by allowing for the imaging to be accomplished in a thin, top layer, providing for enhanced resolution and improved CD control and depth of focus, as compared to single layer resists. Subsequently a transfer process allows the conveyance of this image through a generally thicker, underlying layer, or layers. The use of two, or more, layers allows the decoupling of imaging resolution and aspect ratio. Using an anisotropic reactive ion etch (RIE) further prevents the toppling of high aspect ratio images that is sometimes encountered with solvent or aqueous base development and rinsing processes. The use of a relatively thick underlayer that is independent of imaging chemistry concerns allows for a degree of independence from swing curve phenomena, and thus allows nearly any thickness of underlayer to be used. Consequently, high aspect ratio images can be printed with extended process latitude. Furthermore, the use of an underlayer allows for planarization over underlying topography.
Current underlayer formulations used in bilayer lithography consist of either a novolak resin dissolved in an appropriate casting solvent or a multicomponent system comprising a base polymer and various additives, each of which serves a particular role in the insolubilization of the resulting films. Both types of underlayer formulations have limitations. Novolak-based systems are simple in that they consist merely of a polymer dissolved in solution. However, the optical properties of these materials have been shown to vary dramatically with variations in processing conditions, resulting in nonrobust antireflective properties. Furthermore, the mechanisms of the crosslinking reactions need for insolubilization are not well understood and difficult to characterize.
The multicomponent systems have been demonstrated to improve the optical robustness in terms of processing conditions and provide excellent etch resistance and planarization properties. However, multicomponent systems sometimes suffer from incompatibility of the constituent materials or immiscibility of additives within the polymeric matrix. This may manifest as shelf-life instability and the formation of particles with prolonged storage. Furthermore, the addition of low molecular weight species to underlayer formulation allows for the potential for diffusion of these species into a subsequently applied imaging layer, thereby leading to intermixing of layers and the degrading the performance of the overall film stack.
The present invention addresses these problems experienced in prior art bilayer lithographic systems by providing multifunctional polymers that include chromophore groups as well as crosslinking sites.
The present invention makes possible improved resist structures and especially those multilayer resist structures.
More particularly, the present invention makes it possible to provide resist materials exhibiting desirable optical, physical and chemical properties which can be tuned to the desired imaging wavelength.
The present invention is specifically concerned with a multifunctional polymer comprising a polymeric chain having chromophore groups and crosslinking sites.
Another aspect of the present invention relates to a method for forming a pattern of a resist. The method comprises:
a) providing on a substrate a layer of a resist comprising a multifunctional polymer comprising a polymeric chain having chromophore groups and crosslinking sites;
b) imagewise exposing the resist to actinic radiation in a pattern to thereby cause a change in the solubility of the resist; and
c) developing the resist to thereby form the pattern.
A still further aspect of the present invention relates to a method for forming a pattern which comprises:
a) providing on a substrate a layer of a first resist comprising a multifunctional polymer comprising a polymeric chain having chromophore groups and crosslinking sites;
b) at least partially crosslinking the first resist;
c) providing on the first resist a second and different resist composition;
d) imagewise exposing the first and second resist composition to actinic radiation;
e) developing the second resist composition;
f) developing the first resist; and
g) etching the substrate using the first resist and second resist as the mask to form the pattern.
Still other objects and advantages of the present invention will become readily apparent by those skilled in the art from the following detailed description, wherein it is shown and described preferred embodiments of the invention, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, without departing from the invention. Accordingly, the description is to be regarded as illustrative in nature and not as restrictive.